We've all heard the statistics: Every year, more than 20,000 Americans die on the nation's highways, while at worst a few hundred die aboard planes.So why are so many people afraid to fly?

Is there an air passenger alive who hasn't felt, at some point in the turbulence of a frequent flying career, that the cushion of air between an airplane and the ground is simply not soft enough for comfort?

These feelings, little evolutionary reminders that human beings are not lighter than air, become more nagging at times such as the past few months, when planes have seemed to fall willy-nilly from the skies.

They haven't, of course. Crash deaths are still infinitesimal compared with the number of passengers flying. And Americans are continuing to fly more than ever: 28 million passengers are expected aboard U.S. commercial flights this holiday season, according to the Air Transport Association.

But a spate of bad news from the airline industry has shaken consumer confidence this fall. Just last week:

- On Tuesday, an American Eagle turboprop crashed in North Carolina, killing 15 people.

- On Thursday, American Eagle grounded planes in the Midwest so that pilots could get more cold-weather training, a concern that arose after a plane crashed in icy weather Oct. 31 in Indiana, killing all 68 aboard. Also, Kiwi International Air Lines suspended its 42 daily flights after federal inspectors raised questions about the airline's pilot training.

- On Friday, the FBI said it was investigating recent vandalism of several Tower Air jumbo jets in New York.

All this has been enough to give even the most seasoned air travelers a pinch of apprehension.

Jerilyn Ross, who treats fear of flying at her Ross Center for Anxiety and Related Disorders in Washington, said even she can't help but feel a little anxious after hearing so much bad news about air travel.

"I think each time we hear it, we have to wrestle with ourselves . . . and I think each time it wears down our confidence level," Ross said by telephone from Puerto Rico, where she had flown to attend a convention.

Ross knows all about the statistics. "Statistically, you have a higher chance of dying in a bathtub," she said.

You also have a far greater chance - dozens of times higher - of dying in a car accident than aboard an airplane.

"The biggest thing, the most important factor, is that when people walk on a plane they give up a perceived sense of control," Ross said.

In a car, there's a sense - however illusory - of control. Even on a bus or train, she said, people have the sense that they could somehow escape if they had to.

On a plane, escape is not an especially attractive option.

This gets into the other big issue surrounding air travel: gravity. As Ross put it, "There are things that we, as humans, are not evolutionally prepared for."

The fear of flying is built on several gut-level fears, according to Reid Wilson, a clinical psychologist who designed a take-home kit, "Achieving Comfortable Flight," to help people overcome their fear of flying.

"The fears that we face on a plane are very primitive fears," he said. "Fear of being trapped, fear of being out of control, fear of heights."